use Modern::PBP::Perl;

my $aref = [1, 6, 2, 2, 7, 1, 6, 99, 99, 7, 1, 2, 6, 9, 8, 6, 5];
my @copy;
my @stack;

(($_ == 6 .. $_ == 7) and push @stack, $_) or (push @copy, $_ and @stack=()) for @$aref;
push @copy, @stack;

use Data::Dumper;
print Dumper \@copy;